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T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

Posted: Sat May 02, 2020 6:58 pm
by Reagle
Had this machine upgraded in 2016 (viewtopic.php?f=68&t=122281&p=789484#p789484) and it's been mostly fine, but every so often screen would just go blank after windows starts. If I connect external monitor it would come back and run on the LCD at the wrong resolution. I started poking at it and realized the B140HAN01.2 panel I put in did not have Lenovo specific info in its EDID so it runs generic Windows 10 drivers and occasionally get miss-configured.
After much googling I found out that EDID data can be rewritten under Linux to that of Lenovo version of the same panel. Trouble is I am not able to find the EDID chip on any i2C buses.
This is using Ubunutu 20.04 live image,
get-edid scans all buses and finds no EDID at all
i2cdetect sees i915 gmbus panel on I2c-3 bus
edid-rw does not see the chip there

Any idea why none of tehse tools can see the panel? Somehow in windows under moninfo I can get most of what's in it

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

Posted: Sun May 03, 2020 1:49 am
by RealBlackStuff
Not all LCDs have an EDID-chip.

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

Posted: Sun May 03, 2020 7:34 am
by Reagle
How is the system detecting the panel though? It knows enough to say it' AUO and use the correct timing most of the time.
Or am i chasing the wrong issue and something else makes windows 10 confused with this?

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

Posted: Sun May 03, 2020 10:41 pm
by Reagle
Never mind, I found the answer- these are eDP panels, so they do not expose EDID data externally over I2C like older LVDS panels did.
They use an Aux channel of eDP to send all this data. So the EDID eeprom is still there but is accessed differently.
I suppose reflashing it directly might be an option.
See http://www.vesa.org/wp-content/uploads ... 10-v3.pdf pages 8 and 10

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

Posted: Sun Nov 01, 2020 4:20 pm
by Reagle
Update: gave up and tried buying a different panel. First try was a generic clone from one of the US LCD places. That was nowhere near the color gamut and angle of the original. I then found a Chinese seller who actually had old stock (2013) of Thinkpad FRU 04X0436 B140HAN01.2. So I decided to give it a try. Took about three weeks to arrive but it actually got detected first as Monitor\AUO123D and then as Monitor\LEN40A3 which is what it should be. So if anybody is still looking- seller's name is https://www.ebay.com/usr/screengoodall

I might put my old B140HAN01.2 up for sale- it's not configured for Lenovo but when it does get detected it works fine. Might be power management thing as I've had it on for a few months by keeping laptop on AC power and off sleep mode.